1. Field
The present disclosure relates to the field of communications, and in particular to a method and apparatus for measuring a filtering characteristic, pre-equalizer and communication equipment.
2. Description of the Related Art
As the requirements of an optical communication system on low cost, miniature and flexible configuration, optical and electrical bandwidths of a transmitter of the optical communication system are reduced for various reasons. Currently, a problem of narrow bandwidth may be overcome by using pre-equalization, pre-distortion and pre-emphasis technologies in a digital domain.
FIG. 1 is a schematic diagram of a transceiver in the prior art using the digital pre-equalization technology. As shown in FIG. 1, the transmitter 100 includes an emitter 101, a pre-equalizer 102, a digital-to-analog converting module 103, a laser 105, an optical modulator 104, an optical coherent demodulator 106, an local laser 107, an analog-to-digital converting module 108 and a receiving device 109, the optical modulator 104 including a pluggable interface, and an electrical driving amplifier, etc. Wherein, the emitter 101 emits digital electrical signals, the pre-equalizer 102 pre-compensates for a filtering damage to the emitted digital electrical signals brought about by subsequent filtering modules of the transmitting end, such as the digital-to-analog converting module 103 and the optical modulator 104, the compensated digital electrical signals are converted into analog electrical signals after passing through the digital-to-analog converting module 103, and optical signals are outputted after the analog signals are modulated by the optical modulator 104. The outputted optical signals are demodulated into analog electrical signals by the optical coherent demodulator 106, and the analog electrical signals are converted into digital electrical signals by the analog-to-digital converting module 108, and the receiving device 109 receives the above digital electrical signals. Here, the filtering damage brought about by the subsequent modules after the pre-equalizer 102 in the transceiver, i.e. the digital-to-analog converting module 103 and the optical modulator 104, is referred to as a filtering characteristic of a transmitting end.
Currently, a common frequency domain or time domain method may be used for pre-equalization, and a coefficient of a pre-equalizer may be obtained by using many methods in the prior art, such as zero forcing, and minimum mean square error, etc.; however, a filtering characteristic of a transmitting end needs to be known to these methods.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art of the present disclosure.